Topological magnetoplasmon

Abstract

Classical wave fields are real-valued, ensuring the wave states at opposite frequencies and momenta to be inherently identical. Such a particle–hole symmetry can open up new possibilities for topological phenomena in classical systems. Here we show that the historically studied two-dimensional (2D) magnetoplasmon, which bears gapped bulk states and gapless one-way edge states near-zero frequency, is topologically analogous to the 2D topological p+ip superconductor with chiral Majorana edge states and zero modes. We further predict a new type of one-way edge magnetoplasmon at the interface of opposite magnetic domains, and demonstrate the existence of zero-frequency modes bounded at the peripheries of a hollow disk. These findings can be readily verified in experiment, and can greatly enrich the topological phases in bosonic and classical systems.

Infrared Topological Plasmons in Graphene

“…In phononic realizations, the attainable gyrational frequencies limit operation further still, to the range of kilohertz [12]. Towards optical frequencies, proposals of dynamic index modulation [13] and optomechanical coupling [14] are promising but experimentally challenging to scale to multiple coupled elements [15][16][17].Recently, Jin et al [18] pointed out that the well-known magnetoplasmons of uniform 2D electron gases [19,20] constitute an example of a topologically nontrivial bosonic phase hosting unidirectional edge states. However, as the topological gap exists only below the cyclotron frequency ω c , the spectral operation remains limited to low frequencies.…”

“…Recently, Jin et al [18] pointed out that the well-known magnetoplasmons of uniform 2D electron gases [19,20] constitute an example of a topologically nontrivial bosonic phase hosting unidirectional edge states. However, as the topological gap exists only below the cyclotron frequency ω c , the spectral operation remains limited to low frequencies.…”

“…The plasmonic properties of a general graphene domain r ∈ Ω ⊆ R 2 under an external magnetic field B ¼ Bẑ is described by a linear eigenvalue problem with three field components: the scalar potential Φ and the surface electric current density J ≡ J xx þ J yŷ [18]. For an eigenstate indexed by ν and frequency ω ν , this eigenproblem is specified by [37] …”

Topological Exciton Bands in Moiré Heterojunctions

“…The bulk topological bands lead to chiral edge states, which can support unidirectional transport of excitons optically generated on the edge. Our study therefore suggests a practical new route to engineer topological collective excitations which are now actively sought [32][33][34][35][36][37] in several different contexts.Exciton Potential Energy-For definiteness we consider the common chalcogen TMD bilayer MoX 2 /WX 2 with a small twist angle θ and an in-plane displacement d. TMDs with a common chalcogen (X) atom have small lattice mismatches (∼ 0.1%), which we neglect to simplify calculations. Because of the van der Waals heterojunction character and relative band offsets, both conduction and valence bands of MoX 2 and WX 2 are weakly coupled across the heterojunction.…”

“…The bulk topological bands lead to chiral edge states, which can support unidirectional transport of excitons optically generated on the edge. Our study therefore suggests a practical new route to engineer topological collective excitations which are now actively sought [32][33][34][35][36][37] in several different contexts.…”